Most current exterior vehicular trim components are fabricated from talc-filled polypropylene and thermoplastic polyolefin (“TPO”) materials. Weight reduction and increased use of sustainable, recyclable materials are goals of vehicular manufacturers. Options to integrate recyclable materials into vehicle designs include selecting various recyclable materials with demonstrated mechanical, thermal and other properties that are comparable to the non-recyclable constituents employed in current trim components and parts. Primary options for reducing weight of plastic parts and components in vehicles include reducing the thickness of the parts and components and reducing the density of the materials employed in such parts and components.
While conceiving of trim component designs with reduced part thickness can be relatively straightforward, producing and implementing such designs in vehicles is challenging. In many cases, the strength and stiffness of the materials employed in such designs must be increased to accommodate the reduction in wall thickness. Yet adding high-stiffness constituents to these designs and modifying the materials to improve their strength often results in a significantly less-manufacturing-friendly product, particularly in view of tool wear and the aesthetics of the surfaces of these products.
In general, polymeric materials with recyclable polymeric and non-polymeric constituents have lower flow rates associated with molding operations in comparison to materials employing all or mostly all virgin, non-recycled materials. The melt flow rate of recycled thermoplastic materials is an average of the melt flow rate of its constituents. Given their relatively lower flow rates, polymeric materials with high percentages of recyclable materials can be limited in terms of their integration within vehicular component designs with reduced wall thicknesses.
As noted earlier, most vehicular trim components and parts employ talc-filled polypropylene and talc-filled TPO formulations. Vehicular trim components often employ about 10% to about 40% talc by weight as a filler material. Talc, and other fillers, acts to increase the stiffness and strength of these components. Talc also controls and stabilizes the thermal expansion of these components. Further, talc can act as a nucleating agent for enhancing and accelerating the solidification of these materials during manufacturing within product molds employed to fabricate such vehicular trim components.
Talc as a filler within polymeric vehicular components presents several disadvantages. Talc has a density of about 2.6 g/cm3 and polypropylene has a density of about 0.9 g/cm3. As such, the inclusion of talc in polypropylene vehicular components serves to increase the overall density of the component containing talc as a filler material. Talc also reduces the aesthetics of many vehicular components, particularly at its surfaces. When talc is employed as a filler material in a vehicular polymeric material, its use can reduce the ductility and flow rate of the material during manufacturing.
Other reinforcing filler materials, such as glass, can be used in vehicular trim components with some success in stiffening them with a goal of overall weight reduction. Yet glass has many drawbacks when employed in polymeric vehicular components as a filler material. As glass has a higher density than talc, it can serve to increase the overall weight of a vehicular component in which the talc is replaced with equal parts glass. As glass frit, particles, fiber and the like possess relatively high modulus values, polymeric materials containing glass filler materials can be abrasive. With increased percentages of glass materials, the manufacturing of glass-containing polymeric materials tends to result in shorter tool lifetimes.
Accordingly, there is a need for polypropylene-based compositions suitable for vehicular trim components, and designs of such components, with reduced weight and higher percentages of recyclable materials at current component-neutral cost and performance.